In a machine, such as a wheel loader or track type tractor, for example, an engine supplies power for propelling the machine in the forward or reverse directions as well as supply power for machine implements. A transmission is coupled to the engine and transmits power from the engine to the drivetrain to propel the machine. It is desirable to utilize a continuously variable transmission and manage the transmission ratio to thereby save engine power for the implements and also to provide a continuously variable power flow through the transmission to improve machine productivity. Because machines operate at relatively low speeds and in cyclical work routines, there is a need to control speed precisely at low speeds and to be infinitely adjustable throughout the full range. One of the problems associated with such an arrangement is to match the hydromechanical transmission arrangements to the type of work being performed by the machine using a transmission having four members and two planetary gear sets.
The present invention is directed to overcoming one or more of the problems as set forth above.